The Impact of Fluorination on the Design of Histone Deacetylase Inhibitors

In recent years, histone deacetylases (HDACs) have emerged as promising targets in the treatment of cancer. The approach is to inhibit HDACs with drugs known as HDAC inhibitors (HDACis). Such HDACis are broadly classified according to their chemical structure, e.g., hydroxamic acids, benzamides, thiols, short-chain fatty acids, and cyclic peptides. Fluorination plays an important role in the medicinal-chemical design of new active representatives. As a result of the introduction of fluorine into the chemical structure, parameters such as potency or selectivity towards isoforms of HDACs can be increased. However, the impact of fluorination cannot always be clearly deduced. Nevertheless, a change in lipophilicity and, hence, solubility, as well as permeability, can influence the potency. The selectivity towards certain HDACs isoforms can be explained by special interactions of fluorinated compounds with the structure of the slightly different enzymes. Another aspect is that for a more detailed investigation of newly synthesized fluorine-containing active compounds, fluorination is often used for the purpose of labeling. Aside from the isotope ¹⁹F, which can be detected by nuclear magnetic resonance spectroscopy, the positron emission tomography of ¹⁸F plays a major role. However, to our best knowledge, a survey of the general effects of fluorination on HDACis development is lacking in the literature to date. Therefore, the aim of this review is to highlight the introduction of fluorine in the course of chemical synthesis and the impact on biological activity, using selected examples of recently developed fluorinated HDACis.

Horner-Wadsworth-Emmons reaction as an excellent tool in the synthesis of fluoro-containing biologically important compounds

Selective introduction of a double bond motif into a multifunctional organic compound is always a big challenge. The Horner-Wadsworth-Emmons reaction is one of the most reliable, simple, and stereoselective olefination methods, widely used in organic chemistry. To the best of our knowledge, no review article on the application of HWE reaction in the synthesis of fluoroorganic compounds with direct biological interest has been published in recent years. The importance of the HWE reaction should be emphasised due to its simplicity and stereoselectivity. Under mild conditions and in one step, valuable compounds can be obtained. The HWE reaction is primarily a great tool in the synthesis of fluoroolefins that are, among others, peptide bond mimetics. Therefore, it can serve as an indispensable approach to access peptide bioisosteres and, consequently, analogues of numerous enzyme inhibitors. The protocol may be utilized to obtain florinated vinylphosphonate, vinylsulfone or sulfonate derivatives, which exhibit biological activity. In this review article, we would like to summarize the HWE reaction output of the last 12 years (since 2010).